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    <title>Document</title>
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<body>
    <script type="text/javascript">

        const users = {
            Alex: {
                email: 'alex@alex.com',
                skills: ['HTML', 'CSS', 'JavaScript'],
                age: 20,
                isLoggedIn: false,
                points: 30
            },
            Asab: {
                email: 'asab@asab.com',
                skills: ['HTML', 'CSS', 'JavaScript', 'Redux', 'MongoDB', 'Express', 'React', 'Node'],
                age: 25,
                isLoggedIn: false,
                points: 50
            },
            Brook: {
                email: 'daniel@daniel.com',
                skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux'],
                age: 30,
                isLoggedIn: true,
                points: 50
            },
            Daniel: {
                email: 'daniel@alex.com',
                skills: ['HTML', 'CSS', 'JavaScript', 'Python'],
                age: 20,
                isLoggedIn: false,
                points: 40
            },
            John: {
                email: 'john@john.com',
                skills: ['HTML', 'CSS', 'JavaScript', 'React', 'Redux', 'Node.js'],
                age: 20,
                isLoggedIn: true,
                points: 50
            },
            Thomas: {
                email: 'thomas@thomas.com',
                skills: ['HTML', 'CSS', 'JavaScript', 'React'],
                age: 20,
                isLoggedIn: false,
                points: 40
            },
            Paul: {
                email: 'paul@paul.com',
                skills: ['HTML', 'CSS', 'JavaScript', 'MongoDB', 'Express', 'React', 'Node'],
                age: 20,
                isLoggedIn: false,
                points: 40
            }
        }

        //统计在线人数 
        // const keysArr = Object.keys(users)  //字符串.
        // var count = 0
        // keysArr.forEach(
        //     function (item) {
        //         users[item].isLoggedIn == true ? count++ : count

        //     }
        // )
        // console.log(count);



        // 2.统计分数大于50的人数
        // const keyarr = Object.keys(users)
        // var count1 = 0
        // keyarr.forEach(
        //     function (item) {
        //         users[item].points >= 50 ? count1++ :count1
        //     }
        // )
        // console.log('大于50的人数'+count1);

        // 3.查找会MongoDB的人，并打印其名字
        const keyarr1 = Object.keys(users)
        keyarr1.map(
            function (item) {
                users[item].skills.map(
                    function (params) {
                        if(params=='MongoDB'){
                            console.log(users[item]);
                        }
                    }
                )
            }
        )
        // 4.查找同时会：MongoDB， Express，React，和Node 的人，并打印其名字
        const keyarr2 = Object.keys(users)
        const n = ['MongoDB','Express','React','Node'];
        keyarr2.map(
            function (item) {
                const i = n.every(it => users[item].skills.includes(it))
                if(i == true){
                    console.log(item);
                }
            }
        )

    </script>
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